The present invention relates to a process for electrolytically treating aluminum or its alloys in the form of a strip, wire or foil in a continuous manner to color the same.
Heretofore, in order to color aluminum or its alloys in the form of a strip, wire or foil material by an electrolytic treatment, the material accommodated in a receptacle such as a cage is first immersed in an anodizing cell and then in an electrolytic coloring cell by a batch process. However, this process is disadvantageous in that it is inefficient and produces deviations in the quality of products, whereby it is difficult to attain uniformity in quality. Further, in the case where the material to be treated has a thickness below 0.4 mm, it is bent by impact to which it is subjected when taken in and out from an electrolytic solution. For this reason, the thickness of the material to be treated must be greater than 0.4 mm.
Alternatively, there has been a process for coloring aluminum or its alloys in the form of a strip, wire or foil material wherein the material is electrolytically treated in a continuous manner to form an anodic oxide film thereon and then, the anodized material is colored by a non-electrolytic method such as the use of an organic dye and immersion in an inorganic salt solution. However, the colored product according to this process is poor in fastness to light, whereby it is unsuitable for use as an outer cover and the like.